Method for machining bodies of revolution having a circular generatrix

ABSTRACT

This method consists in holding the workpieces in a driving device and imparting two movements of rotation thereto, namely a movement of relative rotation of each workpiece about its axis and a movement of rotation of all the workpieces together with their driving device about the axis of this device which forms a predetermined angle with the axis of the grinding wheel revolving in the opposite direction compared with said device, the workpieces being fed automatically to said driving device, then brought into grinding engagement with the wheel and eventually ejected also automatically upon completion of the continuous machining operation.

United States Patent Beauchet [54] METHOD FOR MACHINING BODIES OF REVOLUTION HAVING A CIRCULAR GENERATRIX [72] Inventor: Jean Beauchet, Annecy, France [73] Assignee: Societe Nouvelle de Roulements, Annecy (Haute Savoie), France [22] Filed: Oct.3l, 1969 [21] App1.No.: 872,968

[30] Foreign Application Priority Data Nov. 6, 1968 France ..172744 [52] US. Cl. 5l/289 R, 51/129 [51] Int. Cl ..B24b 1/00 [58] Field ofSearch ..5l/289 R, 289 S, 129

[5 6] References Cited UNITED STATES PATENTS 2,218,982 10/1940 Cramer ..51/289 R [451 May 23, 1972 Primary Examiner-Lester M. Swingle Att0rneyStevens, Davis, Miller & Mosher [57] ABSTRACT This method consists in holding the workpieces in a driving device and imparting two movements of rotation thereto, namely a movement of relative rotation of each workpiece about its axis and a movement of rotation of all the workpieces together with their driving device about the axis of this device which forms a predetemiined angle with the axis of the grinding wheel revolving in the opposite direction compared with said device, the workpieces being fed automatically to said driving device, then brought into grinding engagement with the wheel and eventually ejected also automatically upon completion of the continuous machining operation.

4 Claims, 4 Drawing Figures Patented May 23, 1972 3,664,067

3 Sheets-Sheet 1 Patented May 23, 1972 3 Sheets-Sheet 2,

Patented May 23, 1972 3,664,067

3 Sheets-Sheet r METHOD FOR MACHINING BODIES OF REVOLUTION HAVING A CIRCULAR GENERATRIX The present invention relates to a method of machining by abrasion or grinding bodies of revolution having a circular generatrix.

A method of grinding bodies of revolution having a circular generatrix is already known which utilizes a Centerless grinder of conventional design operating according to the in line engagement technique and wherein the working grinding wheel is cut to the desired contour of the workpiece, the workpiece being supported by a fixed bar and driven along the working wheel by a driving drum.

In another method, it is known to grind a workpiece by generation along a spherical surface and by using a cupshaped grinding wheel against which the workpiece is retained while causing this workpiece to revolve about an axis converging towards the wheel axis.

However, in the first method mentioned hereinabove the working or grinding wheel is subjected to wear and distortion, so that cutting operations must be performed periodically to regenerate its contour. Besides, as a rule, grinders constructed according to this method are bulky, complicated and scarcely flexible in operation.

Furthermore, the second method mentioned hereinabove, although pennitting dispensing with the wheel cutting operation, is applicable only to the grinding of spherical surfaces, and it is not suitable for the application of a continuous machining technique.

It is the essential object of the present invention to provide a simpler and more flexible grinding method for obtaining bodies of revolution having a wholly or partially circular generatrix, and combining the advantageous features of known in line engagement processes with centerless loading, with those of generation machining processes.

This method is characterized essentially in that it consists in disposing and maintaining a series of workpieces in a suitable driving device, and imparting to these workpieces two movements of rotation, one movement being a relative rotation of each workpiece about its axis and the other a rotational movement of all the workpieces together with their driving device about the axis of this device which form a predetermined angle with the axis of rotation of a grinding wheel revolving in the opposite direction with respect to said driving device, the workpieces being fed automatically to said driving device and caused to contact said grinding wheel having a sphero-concave working surface, and discharged automatically upon completion of the continuous working operation.

Other features and advantages characterizing this invention will appear as the following description proceeds with reference to a preferred form of embodiment of the method of this invention concerning the machining of taper rollers having a circular generatrix and a relatively great radius of curvature, for a taper-roller bearing, this example being given by way of illustration and described with reference to the attached drawing, in which:

FIG. 1 illustrates a few typical examples of workpieces obtainable by the method of this invention;

FIG. 2 illustrates diagrammatically the principle of the method of this invention;

FIG. 3 is a diagrammatic illustration of the device for carrying out this method, and

FIG. 4 illustrates on a larger scale a detailed plan view of a driving cage with the workpieces and the grinding wheel of the device shown in FIG. 3.

FIG. 1 shows by way of example different types of workpieces obtainable with the method of this invention. Thus, a barrel-shaped workpiece a having a relatively short radius of curvature, a cylindrical roller having a full circular generatrix b or a partial circular generatrix c (bulged or raked roller), a taper roller, also in these two versions d and f respectively, and a strongly asymmetric roller e, are shown.

F IG. 2 illustrates diagrammatically the basic principle of the method of this invention, for example in the case of taper rollers having a circular generatrix having a relatively great radius of curvature (P,, P in this case the workpieces are rigid with a plate revolving about an axis OZ and two movements are imparted thereto: i.e., a movement of relative rotation about their axis OX and OX and a movement for rotatably driving the taper rollers about the axis OZ. Since the workpieces P have a circular generatrix, it will be seen that their outer surface consists of a spherical zone of which the means axis is OZ, a radius of curvature R and a center 0. A cup-shaped grinding wheel M revolving about an axis OZ has a working surface S of sphero-concave configuration having likewise a radius R and a center of curvature at 0. By revolving about its axis, the wheel remains tangent to the outer surface of the workpieces in the ground on finished condition (it being obvious that the wheel becomes tangent to the workpiece only when the latter has the desired contour).

The plane of the figure is that formed by the axes of rotation OZ of the grinding wheel and 02' of the plate driving the workpieces P. In this figure:

Dis the length of chord b 17 (b, and b being the centers of the generatrices a, a; and a a merging into the spherical envelope of the two workpieces P and P diametrically opposed in relation to the axis OZ and having their axes in the plane of the figure); f IK is the versed sine of chord b b on radius R; I is the middle point of chord b b H is the orthogonal projection of I on the axis OZ of the grinding wheel. Thus, L= III;

a is the angle formed by the axes OZ and OZ.

Thus, the following relationship is obtained:

It will be seen that R is dependent on the following variable parameters: sin a, L and D. It is therefore only necessary to alter one of these variables for modifying the value of R.

A typical form of embodiment of a device for carrying out the method of this invention is illustrated in FIGS. 3 and 4. In this device the workpieces 8 disposed in the cavities 9 of a driving cage 10 are rotatably driven about their axes O'X in the direction f by the conjugate action of a track 11 and of said driving cage 10. The track 11 revolves in the direction j; at a higher speed than the cage 10 revolving in the same direction. The workpieces 8 are held in engagement with the cage 10 by a resilient device 12 (for example a spring or a jet of fluid under pressure) and also against a circular surface 13 of track 11 by the centrifugal force. Thus the workpieces are driven by the cage 10 under the working area 14 of grinding wheel 6 revolving in the direction j}, opposite to f (the machining is performed in a single pass). In FIG. 4 the automatic feeding of workpieces 8 is shown only schematically by the arrow A, and the ejection of the ground workpieces is denoted by the arrow E.

The adjustment means and details of this device are shown more particularly in FIG. 3. The assembly comprising the grinding wheel 6 and its support 7 is rotatably driven via a transmission 15 from a motor 16 in a supporting bearing 17. This bearing 17 is adapted, under the control of a screw-andnut mechanism 18 driven by means of a crank handle 19, or under the control of any other suitable means known per se, to slide longitudinally in slideways 20 rigid with the frame structure 21 of the machine, this movement being also imparted to the assembly comprising the grinding wheel 6 and its carrier member 7. The spindle 22 of the driving cage 10 is rotatably driven from a motor 23 housed within a tubular shaft 24 rigid with track 11 driven in turn via a transmission 25 from a motor 26 housed in supporting block or plate 27. This assembly, i.e., the cage 10, track 1 l and supporting block 27 can pivot about a pivot pin 28 rigid with a plate 29 and extending at right angles to the plane containing the axis 02 of grinding wheel 6 and the axis 02' of cage 10. The aforesaid plate 29 is movable in a transverse plane in slideways 30 rigid with the frame structure 21 of the machine, under the control of the rod 31 of a piston 32 movable in a fluid-actuated cylinder 33, or through any other means producing the same action.

The radius R can be adjusted according to the abovedescribed principle and to the reference symbols of FIG. 2, by perfonning the following three operations either separately or in combination:

1. The angle a is adjustable by pivoting the supporting bearing 27 about the axis of pivot pin 28 and causing same to engage an abutment 34 of plate 29 by means of a distance-piece 35 having the desired thickness, or by using any other means capable of causing the angle a to be adjusted with a high degree of precision. Then, the supporting bearing 27 is locked to plate 29 by means of tightening members 36 extending through elongated arcuate slots 37, 38 formed in plate 27.

2. The adjustment of L is obtained by actuating the cylinder 33 so as to bring the plate 29 into engagement with an abutment 39 rigid with the frame structure 21 of the machine, a distance-piece or shim 40 of adequate thickness being used to this end.

3. The dimension D, with due consideration for the length of the workpiece to be machined, results from the dimensions of the circular surface 13.

According to the specific nature of the workpieces to be obtained, the track 1 l and cage may also be replaced by similar parts of different dimensions.

Having duly completed these preliminary operations, the grinding wheel is cut with the radius R by securing a suitable cutting device (as a rule a diamond tool) to the cage 10, so that the cutting edge or point follows the generatrix to be ob tained (for example one of points b of FIG. 2).

In order to operate only in the zone 14 (FIG. 4), a slight clearance is provided by pivoting the axis OZ of the grinding wheel very slightly about the line HI extending at right angles thereto and lying in a plane containing the axis 02 of cage 10 (see FIG. 2). Thus, the workpiece can move beneath the first zone of the wheel without contacting same.

This method of providing a clearance is well known per se and currently used, for example in face or end-grinding. This step does not alter in any manner the nature and quality of the grinding work.

The grinding wheel wear is compensated by simply reducing the distance from the grinding wheel to the workpiece carrier, and any re-cutting of the wheel can be dispensed with due to the machining by generation carried out with the method of this invention.

Of course, this invention should not be construed as being limited by the specific form of embodiment described and illustrated herein, since it also includes any modifications and variations that may occur to those conversant with the art, and is applicable to the machining of workpieces other than those illustrated by way of example in the practical form of embodiment and notably in FIG. 1.

The advantages resulting from the implementation of the present invention consist essentially in obtaining means characterized by extremely flexible conditions of use, whereby bodies of revolution having a circular generatrix can be machined by generation (thus avoiding periodic wheel cutting operations) and as a continuous process.

Besides, the fact that the axes of the grinding wheel and workpiece driving plate are not parallel is attended by an oblique cutting promoting the attenuation of the consequences of spindle defects.

Of course, various modifications and variations may be applied to the specific forms of embodiment of the present invention which is shown and described herein, without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. A method of machining workpieces by abrasion and generation bodies of revolution having a circular generatrix with centerless loading, comprising the steps of automatically feeding a series of workpieces to be disposed in a suitable rotating driving device from which they are ejected automatically after the machining, imparting to each of said workpieces a movement of rotation about the proper axis of revolution of the workpiece and bringing said workpieces into grinding engagement with a sphero-concave active surface of a rotating grinding wheel adapted to move along the axis of said wheel, said rotating driving device being in rotation with said workpieces about the axis of said device which forms a predetermined adjustable acute angle with the axis of rotation of said grinding wheel, said driving device rotating in a direction opposite to that of said grinding wheel.

2. A method according to claim 1, wherein the active surface of said grinding wheel has a radius of curvature equal to the radius of curvature of the generatrix of the workpieces in the finished condition thereof.

3. A method according to claim 1, wherein the axes of all workpieces to be machined are convergent to a single and common point on the axis of revolution of said driving device.

4. A method according to claim 1, wherein the speed of rotation of each workpiece to be machined about the proper axis of revolution of said workpiece is higher than the speed of rotation of the workpieces in said driving device about the axis of rotation of said driving device. 

1. A method of machining workpieces by abrasion and generation bodies of revolution having a circular generatrix with centerless loading, comprising the steps of automatically feeding a series of workpieces to be disposed in a suitable rotating driving device from which they are ejected automatically after the machining, imparting to each of said workpieces a movement of rotation about the proper axis of revolution of the workpiece and bringing said workpieces into grinding engagement with a spheroconcave active surface of a rotating grinding wheel adapted to move along the axis of said wheel, said rotating driving device being in rotation with said workpieces about the axis of said device which forms a predetermined adjustable acute angle with the axis of rotation of said grinding wheel, said driving device rotating in a direction opposite to that of said grinding wheel.
 2. A method according to claim 1, wherein the active surface of said grinding wheel has a radius of curvature equal to the radius of curvature of the generatrix of the workpieces in the finished condition thereof.
 3. A method according to claim 1, wherein the axes of all workpieces to be machined are convergent to a single and common point on the axis of revolution of said driving device.
 4. A method according to claim 1, wherein the speed of rotation of each workpiece to be machined about the proper axis of revolution of said workpiece is higher than the speed of rotation of the workpieces in said driving device about the axis of rotation of said driving device. 